TEM-study of the precipitation of iron in Nd-Fe-B sintered magnets

The microstructure of sintered Nd-Fe-B magnets is studied by analytical electron microscopy. The presence of Fe-rich precipitates was first found in magnets showing a small kink in the demagnetization curve, which is an evidence for soft magnetic nucleation centers for reversed magnetic domains within the magnet. alpha -iron precipitates occurred outside as well as within the hard magnetic 2:14:1 grains and were also found in other commercial-grade magnets with a nominal composition close to Nd15-Fe77-B8.<
>